A customer premise equipment (Customer Premise Equipment, hereinafter briefly referred to as CPE) is connected to an access node (Access Node, hereinafter briefly referred to as AN) by using various access technologies such as a digital subscriber line (Digital Subscriber Line, hereinafter briefly referred to as DSL) or a passive optical network (Passive Optical Network, hereinafter briefly referred to as PON) technology; and one or more metro Ethernet switches (Metro Ethernet Switch) aggregate uplink traffic of multiple ANs to a broadband network gateway (Broadband Network Gateway, hereinafter briefly referred to as BNG). The BNG implements a function of controlling access of the CPE: only when a CPE is legal, the BNG forwards uplink traffic of the legal CPE to an aggregation router (Aggregation Router), and the aggregation router sends the uplink traffic of the legal CPE to an Internet protocol (Internet Protocol, hereinafter briefly referred to as IP) network. Likewise, downlink traffic from the IP network to the CPE is also controlled by the BNG.
When the BNG dynamically allocates an address for the CPE, the BNG also manages multiple address pools for allocating an IP address for a legal CPE.
A layer 2 Ethernet network exists between the AN and the BNG, and in order to ensure isolation of traffic of different CPEs between the AN and the BNG, the AN marks an uplink Ethernet frame of the CPE with a layer 2 virtual local area network tag (Virtual Local Area Network tag, hereinafter briefly referred to as VLAN tag) that uniquely identifies the CPE, which is a service virtual local area network tag (Service VLAN tag, hereinafter briefly referred to as S-vlan tag) and a customer virtual local area network tag (Customer VLAN tag, hereinafter briefly referred to as C-vlan tag). The BNG recognizes traffic of different CPEs through the S-vlan tag and the C-vlan tag, and forwards, to the IP network, an IP packet from which the S-vlan tag and the C-vlan tag have been removed; for a downlink packet from the IP network to the CPE, the BNG adds the S-vlan tag and the C-vlan tag to the downlink packet to generate an Ethernet frame, and sends the Ethernet frame to the AN. Likewise, the AN recognizes, through the S-vlan tag and the C-vlan tag, Ethernet frames sent to different CPEs, and sends, to the CPE, the Ethernet frames from which the S-vlan tag and the C-vlan tag have been removed.
However, in the prior art, BNGs separately provide an access service for CPEs, so that when a BNG is faulty, no other BNGs provide an access service for the CPE originally accessing the faulty BNG, resulting in low reliability of the entire network.